E-Stop & Flight Termination

Comet Vehicle & Operator Units

Comet is a radio-linked remote-stop or flight termination system with digital, pyrotechnic, CAN-FD, serial, and Ethernet outputs. Designed to ensure no single failure shall cause termination, Comet comes with dual redundant processing and redundant termination circuits. Both the Comet Vehicle and Operator units come with dual Ethernet or dual CAN-FD telemetry links which can be used as a soft source of termination information and source of system diagnostics.

In the standard configuration, a single Vehicle unit supports up to two Operator units in line-of-sight operation. Mesh and repeater options allow beyond-line-of-sight operation and range extension. Protocol extensions allow up to eight Operator units.

A socketed radio solution allows Comet to support many popular bands from 400 MHz to 2.4 GHz and transmit power of up to 4 Watts. Licensed and unlicensed variants are available depending on the country of operation.

Interface Control Document

The Comet Vehicle unit has two termination outputs which can be independently configured for positive-logic digital or pyrotechnic ignition function. Termination voting can happen internally or externally, and the output can optionally be latched and held-up for a short period of time.

The Comet Operator unit comes standard with an 8-hour battery, neck lanyard, daylight visible LEDs and a loud buzzer; allowing range safety officers to operate from any location. A rubber duck antenna and neck lanyard is provided as standard, but the unit is also capable of fix location operation via the EN-4165 connector, which can also provide telemetry.

Termination Chain


Microhard Pico Series
Time shared between processors, independent signing keys


Dual Independent STMicro STM32H7
400MHz ARM Cortex M-7 with Double Precision Floating Point Unit
2MB Internal Flash
1MB Internal RAM


Each termination lane has independent Arm, Terminate, and Safe logic assemblies. This structure allows each lane to vote with logical AND, OR, or be lane independent.

Single lane voting topology

External to System

Option 1
Dual 10/100 Ethernet
Single RS-232

Option 2
Single 10/100 Ethernet
Single RS-232

Between Lanes

Optional UART connection between processor lanes for more complex voting and status sharing algorithms.

RF Performance

Band TX Power (W) Sensitivity (dBm) Range (km)
400 MHz 2 -114 110
840 MHz 2 -114 50
866 MHz 1 -114 35
869 MHz 0.5 -112 20
900 MHz 1 -110 20
2.4 GHz 1 -112 10

Range is an estimate and assumes clear line of sight, uniform radiation patterns, 1km receiver altitude, 20dB link margin, and default link rates, bandwidths, and error correction. Real world performance depends on many additional factors.



Vehicle Unit: 375g


Vehicle Unit
Length: 5.9 inches
Width: 4.4 inches
Height: 1.6 inches
Modified Hammond 1590BB

Operator Unit
Modified Hammond 1590KK


Vehicle Unit
4x countersunk chamfered slots
1x counter sunk electrical bonding stud

Operator Unit

Custom base plates for mounting and electrical bonding are possible.


Input Voltage

Vehicle Unit
18 to 30V (nominal)
DO-160G §16.6 Category B

Operator Unit
25.2V maximum charge voltage

Power Consumption

5W typical, unterminated
Meets DO-160G §16.7.5, Inrush


Both types of Comet unit have dual power inputs, internally ORd together with ideal diodes and clamped. This is a common power input feeling a set of shared holdup capacitors and regulators.

Termination power can either be jumped directly to the ORd input rail without clamping and holdup, or after the clamp with holdup.


Comet FTS was subjected to formal environmental qualification testing. For more information, please contact allocortech.


Vehicle Unit:
DO-160G §4.5 Category B2
DO-160G §5 Category B

Operator Unit:
DO-160G §4.5, with minimum temperature of -20°C and maximum of 60°C due to internal battery.
DO-160G §5, with restricted temperature range as above.

Condensing Humidity

DO-160G §10.3.1


Vehicle Unit: DO-160G §8 Category R/Fixed-Wing

Operational Shock

Vehicle Unit: DO-160G §7.2 Category A


Vehicle Unit: DO-160G §4.6.1 Category B2 (-5k to 25k ft MSL)
Operator Unit: DO-160G §4.6.1 Category B2 (-5k to 8k ft MSL)

Induced Susceptibility

Vehicle Unit: DO-160G §19.3.3 and §19.3.4 Category CW

Drop Resistance

Operator Unit: Operating survival of 7 foot drop onto any corner and any face





Internal JTAG Header, RS-232 ST Bootloader, allocortech bootloader over CAN, RS-232, or Ethernet

allocortech has many supported custom configurations of the Comet that can be created upon request.  The base part numbers are listed here:

  • 100-0050-001 —
    COMET FTS Vehicle Unit (Air) ERHHSSLLDD900
  • 100-0050-002
    COMET FTS Vehicle Unit (Air) CPHHVVTTDD900
  • 100-0050-003
    COMET FTS Vehicle Unit (Air) EPHHSSLLDD900
  • 100-0050-104
    COMET FTS Vehicle Unit (Air, Mark II) CPHHVVTTDD9005
  • 100-0050-105
    COMET FTS Vehicle Unit (Air, Mark II) CPHHVVTTDD4005
  • 100-0050-106
    COMET FTS Vehicle Unit (Air, Mark II) CPIIVVLLDD4005
  • 100-0051-001 —
    COMET FTS Operator Unit (Mark I) EPHHSSTTDD900
  • 100-0051-101 —
    COMET FTS Operator Unit (Mark II) EPHHSSTTDD9005
  • 100-0051-102
    COMET FTS Operator Unit (Mark II) EPHHSSTTDD4005